Method and apparatus for hydroponic gardening

ABSTRACT

Plants are hydroponically grown in a cellular water table provided with divergent grow lines along which plants are moved in plant holders. The grow lines are arranged to provide spacing between adajcent rows of plants as plants mature. Within each grow line is a variable pitch screw arrangement which provides for increased spacing between adjacent plants in a grow line as the plants mature. Four-way spacing is provided for both the leaves of the plants and their roots as the plants are suspended over the cellular water table. Maintenance of the system is facilitated by a crawl space beneath the water table which allows access to removable bottom panels of the individual cells within the water table. Plants are cultivated and serviced from the top by a man carrier system. CO 2  enriched air and/or pesticides are supplied directly to the undersides of the plants by a conduit system provided within each grow line. Nutrient enriched water is provided to the roots of the plants by a closed loop fluid circulation system.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 198,447,filed on May 25, 1988 now U.S. Pat. No. 4,932,158.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention involves the field of technology pertaining to thegrowing of plants hydroponically, i.e., with enriched water and air. Theinvention relates to a method and apparatus for optimizing the yield perhydroponic greenhouse by controlling all of the variables which affectplant growth and to maximize greenhouse space utilization.

2. Description of the Prior Art

A common problem in many hydroponic plant growing operations is that theamount of space between individual plants is fixed and maintained fromthe date of planting until harvesting. This can result in anunderutilization of available growing space and consequently the costsof production are greater than would be the case if available growingspace were used in a more efficient manner.

Most growers of hydroponic products grow plants either in troughs atfixed spacing with nutrient water supplied at one or two places anddrained at one or two ends, or in stationary pots, grow-blocks, or otherdevices providing physical support with the nutrient being dripped on,flowed through, or flowed around the support.

Prior attempts to alleviate the spacing problem in hydroponic farmingare shown in Haub et al U.S. Pat. Nos. 4,337,986 and 4,216,618. Thesepatents disclose a variable pitch screw arrangement for increasing thespacing between plants in accordance with their growth rate. However,these variable pitch screw arrangements are used in conjunction with atrough system in which the troughs are placed in parallel relation toeach other. While this system allows for increased spacing between rows,it does not provide for automatic spacing between adjacent plants withina trough as they grow.

Davis et al U.S. Pat. No. 4,028,847 provides spacing between rows ofplants by the use of a divergent track system. Young plants are firsttended in growth chambers and then moved to tracks or troughs. Thissystem does not provide for increased spacing between adjacent plants asthey mature.

Another known system uses divergent troughs with a variable pitch screwarrangement which moves the plants along the troughs at graduallywidening x-y spacings as they grow. This method provides appropriatespace for leaves, but not for roots, which are confined within theavailable space of the trough. The roots tend to dam the free flow ofnutrient water, causing the roots to turn brown, harbor disease, haveless uniform development, etc. In addition, because this system isvirtually inaccessible from the bottom, there is no way of removing sickplants without breaking off the roots, which remain in the trough andbreed more disease.

SUMMARY OF THE INVENTION

The system of the invention is designed to realize the goals of (1)allowing each plant only as much space as it absolutely needs to grow,thereby making efficient use of costly greenhouse space; (2) being ableto change this spacing according to the growth characteristics ofdifferent plant species; (3) supplying air, CO₂, nutrients, water andlight in such a manner that product quality and uniformity are enhanced;(4) being able to apply pesticides only when needed and in such a manerthat little or no residue is left on the plants; (5) providing themechanical capability of cleaning the growing apparatus without takingthe growth areas out of production; and (6) being able to inspect andcull the plants during production. The realization of these six goalsserves to significantly reduce or eliminate some of the traditionalproblems of hydroponic farming, such as wasted space, uneven productquality, and disease and insect infestation.

It is therefore an important object of the present invention to providea method and apparatus for the hydroponic growth of plants whichprovides four-way spacing for roots as well as for leaves, so that bothroots and leaves have just enough growing space according to their stageof development, thereby optimizing the utilization of costly greenhousespace.

The object of the invention is achieved by providing an open gridworkformed by a frame wherein the intersecting frame members defineindividual "cells." Each cell is provided with a removable plasticbottom panel, which is preferably white, and which contains the waterand nutrients within each cell. The framework is constructed within a"module" which is surrounded by a vertical, water-tight, structuralenclosure to contain the water and maintain its level.

Suspended above the cells and resting on blocks on the frame are "growlines," which may be formed from flexible material. These grow lines rundivergently from one end of the module (the starting line) to theopposite end of the module (the harvest line), and carry out the twinfunctions of spreading out the plants as they grow and providing thegrowing plants with filtered and temperature controlled air, CO₂,nutrients and/or pesticides, as required. At the center of each growline is a variable pitch screw to which plant holders are attached andwhich moves the plants when turned. The pitch of the screw is selectedto correspond to the expected growth of the plants in the system. Aplastic housing or extrusion surrounds the variable pitch screw andcontains a system for carrying air which is enriched with CO₂, nutrientsand/or pesticides to the plants. These ingredients, which are criticalfor successful plant growth, are directed at the underside of the leavesof the plants by a piping system contained within the plastic housing ofthe grow lines.

The ability to circulate the enriched air directly through the plantleaves is an important advantage in growing the plants rapidly. Airmovement is also important to the growth of plants because itfacilitates transpiration, plant cooling and uptake of carbon dioxide.The present invention provides for sterilized air, blown up through theleaves instead of over their tops, which air is adjusted for temperatureand humidity. Furthermore, the ability to jet gaseous pesticides on theunderside of the plant leaves, where insects are most often found, andonly when needed, is a more effective means of controlling insect peststhan traditional pesticide application, and minimizes residual particleson the leaves.

Plant holders are supported by and moved along the grow lines forcontaining individual plants which remain in the holders from seed toharvest. After germinating and growing in a nursery in the plant holderfor an initial period, a group of seedlings is transferred to the growlines with each plant holder being disposed in the plastic housingcontaining the variable pitch screw. The screw spaces the plant holdersaccording to the growth curve of the plant as it moves them fromstarting point to harvest. If, at any point, an inspection indicatesthat a plant is sub-normal, the entire plant holder can be disassembledin place and the entire plant, including roots, removed, therebyreducing the possibility of spreading disease.

Each plant, therefore, begins at the starting line, at which point thefirst cell contains the appropriate nutrients for seedling growth. Theroots of the plants are suspended in the water contained in the firstcell. As the plant grows, the variable pitch screw within the grow linelongitudinally separates the plant from its adjacent plants, while thedivergent arrangement of the adjacent grow lines provides lateralseparation of the plants. The roots of the plant pass from one cell tothe next as the plant matures and each subsequent cell contains theappropriate proportion of nutrients for the stage of growth of theplants. The roots are therefore permitted not only the optimum amount ofnutrients at each stage of growth, but also four-way spacing betweenplants as they mature.

Within each rectangular module, one half of the grow lines are arrangeddivergently from starting line to harvest line. The other half of thegrow lines diverge in the opposite direction, defining a sister half ofthe module, thus improving the efficiency with which space is used inthe greenhouse.

The grow lines are preferably curved in their midsections, the curvatureof which is correlated with the growth curve of the plants and theavailable greenhouse space to optimize utilization of same. The growlines are rendered flexible by the selection of appropriate conventionalconstruction materials and by their small cross-sectional diameters(about 2") compared to their preferred lengths (over 100', preferably124' to 128'). The curvature of the grow lines ideally corresponds tothe growth curve (plant size vs. age) of the particular crop. The firstsection, preferably the first one quarter, of each module contains growlines which are parallel and close together from the starting line onone side of the module (because the daily increase in size of the plantis small when the plant is a seedling), and grow lines which areparallel and more widely spaced to the harvest line on the other side ofthe module (because at maturity the more widely spaced plants occupy alength of grow line equivalent to a number of days as seedlings). Themidsections of the grow lines are curved according to the growth curveof the crop. The end section of the module is the reverse image of thefirst section. Thus, each end of the module contains spaced, parallelgrow lines which contain plant holders with young plants. The grow linesbegin to curve after a specified number of days to allow for four-wayspacing of leaves and roots for each plant and to maximize the efficientuse of the greenhouse space. After the plants have reached a certainsize, their growth is less rapid and the grow lines are once againconfigured in parallel relation for the final period of growth andharvesting. Each end of the module, therefore, incorporates the morewidely spaced, parallel grow lines, at the ends of which harvestingtakes place.

Nutrients are supplied to each cell within each module by a nutrientsupply arrangement, which may employ any conventional fluid circulationsystem. The invention delivers moderately-to-briskly moving, temperaturecontrolled, sterilized water with balanced nutrients to each cell. Themoderate-to-brisk movement of the nutrient water within each cell helpsto keep the roots of the plants clean, healthy and pleasantly white. Italso assures a full strength supply of nutrients and removes toxic plantwastes. Nutrient and pH levels are continually checked and replenished.

Each individual cell within each module may be accessed by laborers ondollies in a crawl space below the framework of the cellular watertable. When it becomes necessary to clean a particular cell, the waterlevel within the individual cell is lowered by opening a drain which isprovided in a removable plastic bottom panel of each cell. When thewater has drained from the individual cell, the plastic bottom panel isremoved, and the cell can be maintained without disturbing plants inother cells within the module. The crawl space also provides forservicing of all piping and duct work.

The growing plants can be maintained from the top without the need foraisles between grow lines. Plants and grow lines are serviced by amobile man carrier supported over the plants. Therefore, where aisleswould be present in traditional greenhouses, the greenhouse space of thepresent invention is utilized by additional grow lines, thus reducingthe per-plant space cost. Tracks are provided along the outside of eachmodule, on which a repair/maintenance truck can ride. From this truck,the operator can remove diseased plants, replace light bulbs, andperform any maintenance at plant level and above.

The present invention further incorporates a lighting system for thecells wherein light fixtures may be moved directly over the plants onovercast days and out of the way on sunny days. As a result of thisfeature, artificial light can be used efficiently and in tandem withnatural sunlight to encourage efficient plant growth.

The entire apparatus of the invention is surrounded by a conventionalgreenhouse structure having a concrete floor, and a sterile entry.

Other objects, features and advantges of the invention shall becomeapparent from the following detailed description of preferredembodiments thereof when taken in conjunction with the drawings whereinlike reference characters refer to corresponding parts in the severalviews.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the exterior of a green house.

FIG. 2 is a schematic view of the layout of grow lines for one module.

FIG. 3 is a partial section of a cell taken along lines 3--3 of FIG. 4.

FIG. 4 is a fragmented perspective view of a module.

FIG. 5 is a sectional view taken along lines 5--5 of FIG. 3.

FIG. 6 is a section taken at line 6--6 of FIG. 5.

FIG. 7 is a partial sectional view of the greenhouse of FIG. 1.

FIG. 8 is a perspective view of a plant holder.

FIG. 9 is a perspective view of a truck serving as a mobile man carrier.

FIG. 10 is a partial view of an alternate embodiment of the screwhousing shown in FIG. 5.

FIG. 11 is a schematic view of an alternate layout of grow lines for onemodule.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts the exterior of a conventional greenhouse 2 having asterile entry way 4. The sterile entry way 4 allows for laborers tocleanse themselves, following clean room procedures, of any contaminantswhich they may otherwise bring into the hydroponic environment andthereby reduce the risk of disease to the plants. The greenhouse 2 maybe of conventional structure and dimensions, and preferably runs east towest along its length. The greenhouse 2 is preferably provided with apoured concrete floor (not shown) to facilitate maintenance ofgreenhouse hygiene.

FIG. 7 depicts a partial section of the interior of greenhouse 2according to the present invention. The greenhouse 2 is provided withone or more modules 6, each of which is preferably rectangular inconfiguration, and defines a water table or growing area for thehydroponic system of the invention. Module 6 is supported by legs 52over a crawl space 54. A mobile man carrier 90 rides on tracks 91 alongthe longitudinal sides of each module 6, and may bridge the open spacebetween adjacent modules 6. Floor 92, which may be of poured concrete,is intended to promote hygiene within the greenhouse. Suspended abovemodules 6 are a plurality of retractable lights 94 which may be movedover the plants when sunlight is inadequate or unavailable and moved tothe side of the greenhouse when sunlight is abundant or adequate. Lights94 are suspended from a rod 96 by conventional means which facilitatetheir retraction, such as roller and track assemblies. A conventionalair circulation means 98 is also provided within the greenhouse toevaporate spills and prevent air stagnation.

FIG. 2 schematically depicts module 6 according to the invention. Eachmodule 6 may be any desirable length and width, but is preferably about124' to 128' long and about 8' wide. The module 6 contains a pluralityof transverse cells 24 which collectively define a cellular water table.The cells 24 are defined by the structural framework of the module 6 asmore fully discussed below. Supported above the cells 24 and extendinglongitudinally of module 6 are flexible grow lines 8 and 18. The growlines 8 and 18 support the plants which are to be grown in thehydroponic system of the invention, and move the plants from one end ofthe module 6 to the other by means which are more fully described below.

Grow lines 8 and 18 are arranged within the module 6 to optimize spaceutilization, while allowing the individual plants sufficient space fortheir leaves and roots to grow. Grow lines 8 are shown to emanate fromstarting line 10 in a narrower parallel fashion through a section C ofthe module 6. The grow lines 8 then begin to curve slightly according tothe growth curve (individual plant size as a function of age) of thecrop. Table I presents sample calculations (for lettuce) for screw pitchwithin and spacing between grow lines relative to plant size and age("days in grow out").

                  TABLE 1                                                         ______________________________________                                        RELATING PLANT SIZE & AGE                                                     TO SCREW PITCH & DISTANCE                                                     Days                        Cumu-                                             in    Plant  Plant    Screw lative                                                                              Reverse Screw                               Grow- Size   Spacing* Length                                                                              Length                                                                              Cumulative                                                                            Pitch                               out   (in)   (in)     (in)  (in)  Length (in)                                                                           (turns/in)                          ______________________________________                                        1     1      1.50     37.50  37.50                                                                              1536.00 6.66                                2            1.50     37.50  75.00                                                                              1498.50 6.66                                3            2.00     50.00  125.00                                                                             1461.00 5.00                                4     2      2.00     50.00  175.00                                                                             1411.00 5.00                                5            2.25     56.25  231.25                                                                             1361.00 4.44                                6     2      2.25     56.25  287.50                                                                             1304.75 4.44                                7            2.50     62.50  350.00                                                                             1248.50 4.00                                8            2.75     68.75  418.75                                                                             1186.00 3.64                                9            3.00     75.00  493.75                                                                             1117.25 3.33                                10           3.25     81.25  575.00                                                                             1042.25 3.08                                11    3      3.50     87.50  662.50                                                                              961.00 2.86                                12           4.00     100.00                                                                               762.50                                                                              873.50 2.50                                13           4.50     112.50                                                                               875.00                                                                              773.50 2.22                                14    4      5.25     131.25                                                                              1006.25                                                                              661.00 1.90                                15    5      6.25     156.25                                                                              1162.50                                                                              529.75 1.60                                16    6      7.25     181.25                                                                              1343.75                                                                              373.50 1.38                                17    7      7.69     192.25                                                                              1536.00                                                                              192.25 1.30                                ______________________________________                                          *Note:                                                                       At least one day ahead of growth curve. Axial (Longitudinal) plant spacin     is calculated according to size of plant plus room for growth. Lateral        plant spacing (between grow lines) is laid out using the longitudinal         spacing as a guide within the physical confines of the design. Thus, at       planting end, spacing is 2", not 1.5" because of interferences. At harves     it is 6", a width suited to the width of the module and representative of     good commercial production. This parallel 6" and 2" spacing is sufficient     for 1/4 of the length (384") of each end, and the middle half is blended      in to approximate the longitudinal spacing for each day of the growth         curve.                                                                   

As also shown in FIG. 2, the grow lines 8 continue to diverge and curveaccording to the growth curve of the crop through an intermediatesection B of the module 6 until the plants have reached maturity insize. The grow lines 8 then proceed to harvest line 16 in a widerparallel fashion through a section A of the module 6.

Grow lines 18 traverse the module in opposite relation to grow lines 8.Grow lines 18 emanate from starting line 20 in a narrower parallelfashion through section A of the module 6, at which time the grow lines18 begin to curve out to accommodate the growth needs of the plant. Thegrow lines 18 continue to curve out through intermediate section B ofthe module 6. The grow lines 18 again become parallel in wider spacingand proceed to harvest line 22 in this manner through section C of themodule 6. Thus, at each end of the module 6, both harvesting and plantentry into the system take place. These ends form transverse walls ofthe module.

FIG. 4 depicts a fragmented section of module 6 according to theinvention. A pair of opposed longitudinal walls 50 (only one shown) anda pair of opposed transverse walls 58 (only one shown), which may beconstructed of any suitable material, are provided to form the peripheryof module 6. The walls 50 and 58 are supported in a raised position by aplurality of legs 52 which may be any height (preferably about 4') whichallows for a crawl space 54 beneath module 6. The crawl space 54facilitates the maintenance of the system by permitting access to thebottom of the module 6 by laborers on conventional dollies (not shown).All of the piping and paneling of the system may be serviced from crawlspace 54. The legs 52 may be constructed of any suitable material. Thelegs 52 are provided at evenly spaced intervals, preferably about every4', along the longitudinal walls 50 of the module 6 and at the cornersof the rectangle which is formed by the intersection of the longitudinalwalls 50 with the transverse walls 58.

A gridwork of cells 24, each of which may be of any appropriatedimensions, but which are preferably approximately 4' by 8', is formedby extending a plurality of structural members 56 across the width ofthe module 6 in parallel relation to the transverse walls 58 of themodule 6. The structural members 56 are supported by and attached tolegs 52 by conventional means. The structural members 56 form sills 42of the cells 24 parallel to transverse walls 58 of the module. Thelongitudinal walls 50 define the sides of the cells 24. The height ofsills 42 is less than the height of walls 50 and 58 to permit fluidcommunication between cells 24.

Each cell 24 is provided with a removable bottom panel 36 to contain thenutrient enriched water used in cell 24. Within each cell 24 and inparallel relation to structural members 56 and transverse walls 58 ofthe module 6 is provided a closed loop perforated pipe 44 to providerecirculation of nutrient enriched water from a supply line 47. Therecirculation system (not shown) connected to supply line 47 may be anyconventional pumping and storage system. The recirculating systemdelivers a measured mixture of temperature controlled, sterilized waterand balanced nutrients briskly to a plurality of plants 34. The nutrientenriched water is piped from a storage tank (not shown), filtered,sterilized and circulated through the roots of the plants 34. Afterfeeding the plants 34 and washing away plant wastes, the solution ispiped back through perforated pipe 44 to the storage tank, wherenutrients are replenished and the pH level is monitored and adjusted, ifnecessary. When the controlled water is delivered back to the cells 24,it is directed briskly at the roots of the plants 34 by perforated pipe44. The brisk movement of the water promotes the health of the roots andmaintains their natural color. It also efficiently removes toxic plantwastes.

A plurality of support blocks 30, which may be of stepped configurationand formed of aluminum, are situated on structural members 56 to supportgrow lines 8 which are anchored at their opposite ends to transversewalls 58 and driven by a conventional chain drive system 60. The growlines 8 are spaced apart from each other according to the growth needsof the particular crop being raised in the manner previously describedherein. A variable pitch screw 26 is contained within a screw housing28, which may be formed of plastic, within each grow line 8. Thevariable pitch screw 26 is rotated by chain drive system 60 and servesto move the plants 34 which are contained in a plurality of plantholders 32 across the module 6. Plant holders 32 are spaced along thegrow lines 8 according to the growth needs of the particular crop beingraised to provide adequate spacing between adjacent plants 34. Thelongitudinal spacing of the plant holders 32 is effected by the use ofvariable pitch screw 26 in a manner more fully discussed below.

FIG. 3 depicts a partial section of a cell 24 according to theinvention. Flexible grow line 8, incorporating variable pitch screw 26through screw housing 28, is suspended above the cells 24 by supportblocks 30. The pitch of the variable pitch screw 26 is fine at thebeginning of the grow line 8 and gradually expands as the end of thegrow line 8 is approached. Plant holders 32 are attached to the variablepitch screw 26 within screw housing 28. The plants 34 within plantholders 32 are spaced progressively apart from one another as theymature by turning the variable pitch screw 26 either manually or by useof the chain drive system 60 previously described with reference to FIG.4.

The roots of the plants 34 extend into the nutrient enriched water ofthe hydroponic system of the invention. The water level within themodule 6 is substantially controlled by the perforated pipe 44 of therecirculation system within each cell. A plurality of draining means 41are also provided to prevent overflow of the water out of the module 6.Each cell 24 is provided with a removable bottom panel 36, which ispreferably white. A white bottom panel reflects light back up to theplants and maximizes utilization of available light. The removablebottom panel 36 is affixed to the cell 24 by retaining means 38, whichmay be any means known to one of ordinary skill in the art, but which isrepresented herein by a clamping bar. The water level within the module6 is maintained above the sills 42 of each individual cell 24 at thelevel of a plurality of drain holes 39 of draining means 41 duringnormal operation of the system according to the present invention. Thisallows the roots of the plants to reach the nutrient water while beingtransported along the grow lines 8 and 18 without physical interferencefrom the sills 42 of the cells 24. When maintenance of an individualcell is necessary, the water level of the entire module 6 is dropped tobelow the level of the sills 42 by means of recirculation system 44.

Each removable bottom panel 36 is provided with a plurality of celldraining means 40. Each cell draining means 40 includes a downwardlydirected spout 43 to which is attached a hose 45. When the drainingmeans 40 are not desired to be in operation, then hose 45 may be clampedby a conventional clamping means (not shown). When it is desired toclean the cell 24, the water level of the module 6 is lowered to a levelbeneath the sills 42 of the cell 24, as described above. Hose 45attached to spout 43 of the cell draining means 40 is unclamped and thewater within the cell 24 is allowed to drain out of the cell 24. Thebottom panel 36 of the cell 24 is then removed, and the entire cell 24may be cleaned without disturbing the activity in neighboring cells.When the cell 24 has been cleaned, the water level is restored to itsoperating level.

FIG. 5 depicts a section of a grow line according to the invention.Support block 30 is shown supported by structural member 56. Supportblock 30 incorporates draining means 41, a reinforcing support bar 70,which may be of any conventional support material, and an air supplyinlet 72. The reinforcing support bar 70 and the air supply inlet 72extend into the screw housing 28 and along its length, with housing 28being formed of any material, preferably plastic. The reinforcingsupport bar 70 functions to retain the screw housing 28 in place in theapparatus. The air supply inlet 72 is provided with a conduit 74 and aconduit 76, each having a plurality of apertures 75 and 78,respectively.

Conduit 76 delivers CO₂ enriched air to the underside of the plantleaves. The conduit 76 may also be used to apply gaseous pesticides tothe crops grown according to the method of the present invention. Theapertures 78 in the conduit 76 are spaced over short distances such thateach plant 34 in the system is provided with fresh CO₂ enriched airand/or pesticides, as necessary. The provision of CO₂ enriched airdirectly up through the leaves is critical for the prevention ofdiseases which are nurtured by moisture, because the CO₂ enriched airdries the leaves. The provision of fresh air continuously up through theleaves also prevents stagnant air from coating the leaves. CO₂ enrichedair provided directly through the leaf canopy can increase yields by20-30% and can compensate for low light levels.

Plant holder 32 is provided with an engagement means 80 that includes apair of outwardly extending guide ribs 82, which slidingly engage guidegrooves 79 of the screw housing 28, and a horizontal protrusion 83 whichextends through screw housing 28 into sliding engagement with a helicalgroove 81 of the variable pitch screw 26. As seen in FIG. 5, engagementmeans 80 supports holder 32 over the water of cell 24 in a cantilevermanner. As the screw 26 is turned, the plant holder 32 is moved alongthe grow line and spaced progressively apart from its adjacent plantholders 32 by the pitch of the screw 26. Plant holder 32 is secured inits vertical position by guide grooves 79 which collectively define alongitudinal slot in housing 28 that extends for substantially theentire length of screw 26. Engagement means 80 of plant holder 32 may bemade of any conventional low-friction material. A drainage hole 85 isprovided under the guide rib 82 to permit drainage of moisture and othermaterials which may potentially clog guide grooves 79 of screw housing28.

FIG. 6 depicts variable pitch screw 26 with closely spaced plant holders32 engaged with helical groove 81. The arrangement depicted is that ofthe plant holders 32 at the initial stages of the process, wherein thepitch of the screw is fine and the plants are close together. As theplants mature, the plant holders 32 are spaced increasingly fartherapart along the length of grow line 8, due to the change in pitch ofscrew 26. Plant holders 32 allow for the rapid removal of diseasedplants from the system. FIG. 6 further shows a plurality of spacedapertures 78 in air piping system 76 contained in screw housing 28,which direct CO₂ enriched air and/or gaseous pesticides at theundersides of the leaves of the plants along the length of the grow line8.

FIG. 8 depicts plant holder 32 which may be constructed of any suitable,preferably light-weight, material. Plant holder 32 is provided withengagement means 80 extending from a solid first side 100. A second side102, a third side 104 and a snap-on fourth side 106, in conjunction withsolid first side 100, define an open-ended cavity. A die-cut sponge wick110 provided with a slot 111 therein initially contains the germinatingseed (not shown). Wick 110 is inserted into the cavity of plant holder32. The fourth side 106 is detachably secured to sides 102 and 104 by anappropriate snapfit interengagement, shown generally at 112, on bothsides of fourth side 106. As the seedling begins to emerge from thesponge wick 110, the plant holder 32 containing the nascent plant isintroduced into grow line 8 according to the present invention, and ismoved along the grow line 8 in the manner previously described until theplant reaches maturity and is harvested. If it is desired to remove adead or diseased plant from the system, a laborer in mobile man carrier90 can unsnap the fourth side 106 from the plant holder 32 and removethe sponge wick 110 containing the entire plant, including its roots.The removal of the entire plant from the system decreases the spread ofdisease and prevents damming of the water flow in the cellular watertable. The second side 102 and the third side 104 of each plant holder32 are provided with ventilation holes 114 to permit the passage ofoxygen through the plant holder 32 and sponge wick 110, and thus to theroots of the growing plant contained therein. Sponge wick 110 is securedto the plant holder 32 by means of a plurality of spikes 120 providedaround the upper periphery of holder 32 which engage outwardly directedflanges 113 of wick 110.

FIG. 9 depicts mobile man carrier 90 for use in connection with thepresent invention. The mobile man carrier 90 is constructed of wheels150 having a supporting bed 140 attached thereto by conventional axlemeans (not shown).

FIG. 10 depicts an alternate embodiment of a screw housing 28' and aplant holder 32' according to the present invention. Screw housing 28'is provided with a perforated air piping channel 130 which transportsCO₂ enriched air and/or gaseous pesticides along the length of the screwhousing 28'. Air supply inlet 72' provides the enriched air to airpiping channel 130. Channel 130 is provided with apertures 132 whichdirect CO₂ enriched airand/or gaseous pesticides to the underside of theleaves of the plant 34' contained within plant holder 32', as well as tothe underside of the leaves of the plant situated in a like manner inthe adjacent grow line. Plant holder 32' extends downwardly toapproximately the mid-point of support block 30' to provide morepositive movement control.

FIG. 11 depicts an alternate embodiment of the layout of grow lines 8'and 18' within module 6'. Grow lines 8' and 18' are arranged in adivergent pattern over the cellular water table, without incorporatingany curvature in the grow lines 8' and 18'.

The following Example is intended to further describe the invention, butshould not be considered to limit the scope of the invention in any way.

EXAMPLE

Although many flowers, fruits and vegetables can be grown in the systemof the invention, leaf lettuce has been chosen as an example startingcrop. There are a number of reasons for the selection of lettuce as thestarting crop. The production economics are attractive because lettucegrows fast, needs less space, requires fewer production operations,attracts fewer diseases and pests, and most of the fully grown plant isedible.

The greenhouse of the Example contains three modules according to theinvention, each of which incorporates 20-24 grow lines.

Before seeding, die cut sponges are placed in plant holders, the fourthside of the holder is snapped on and the plant holders are arranged in anursery for the germination period. Seeds are placed in slits withineach sponge within each plant holder, and the plant holder is placed ina germination box or in a nursery water table and marked with the date.Depending on the season and the variety of plant, the seedlings stay inthe germination box for 1 day and in the nursery water table for about10-14 days. The seedlings are then culled, placed in a smalltransportable water table, moved to the grow lines of the presentinvention and fed into the slot guides of the variable pitch screwhousing.

At this point, the roots are long enough to reach down from the growline screw housing to the water level. The grow lines are suspended overa cellular water table in modules which may preferably be 8' wide and124' to 128' in length. Each cell is approximately 4' by 8' withremovable white plastic bottom panels for easy cleaning. The whitebottoms also reflect sunlight onto the lower leaves and undersides ofthe leaves to aid growth and enhance product quality, with fewerlight-starved yellow leaves to remove at harvest.

As the plants grow, they need more space. Longitudinal spacing isprovided by the variable pitch screw with comparatively fine threads atthe planting end to very coarse threads at the harvest end, andintermediate pitches according to the growth curve (size, measured inlinear or weight units, vs. days of growth) of the plants. For example,if 25 plants are each about 11/2" by 11/2" when transplanted from thenursery, then the screw pitch is such that when 25 plant holders are fedinto the drive screw, they would occupy approximately 11/2"×25=371/2"longitudinally along a given grow line. Fifteen days later at harvest,plants which are approximately 6" by 6" would occupy 6"×25=150" of growline. The growth curve is different for each variety of plant.

Lateral spacing is accomplished by arranging the grow lines in adivergent pattern over the water table, with plant end spacing at 11/2to 2", fanning out to 6" at harvest end. The lateral spacing of the growlines is also spaced according to the growth curve so that they areapproximately parallel for any particular day's growth, i.e., 2" apartfor the first 50" and 6" apart for the last 150". The roots are not in atrough but are free to spread out, as are the leaves, thereby providingfour-way spacing. This allows the water to pass more freely, without thedamming effect of troughs. It also facilitates cleaning of the roots andallowing them to develop fine hair-like feeders essential for goodgrowth.

To optimize space, 10-12 lines diverge one way and the next 10-12 linesrun in the opposite direction, so both planting and harvestingoperations are occurring simultaneously at both ends of the greenhouse.Because young plants are shorter than harvest size plants, the interfacebetween the two halves of an 8' module may be spaced to reduce anyshading. For example, if the greenhouse runs east-west, the sun passesalong its length shining from the south, most markedly in the winter. Ifa 6" plant is south of an adjacent 11/2" plant, it will throw a shadow.Correct spacing will minimize any such shadow.

As the plants mature, they are supplied with both air and water at thecorrect temperatures over short distances (preferably every 4' to 8')only 2-3 inches from the plants so that the convection of air plusradiation of nutrient water provide good growing temperatures up throughthe plant leaves. Air movement through the leaves is critical to preventvarious diseases and to prevent a layer of stagnant air from coating theleaves.

The plants are spaced within the module as they mature in the mannerpreviously described until harvest (approximately 15 days).

It is to be understood that the forms of the invention herein shown anddescribed are to be taken as preferred embodiments of the same, and thatvarious changes in shape, material, size and arrangement of parts may beresorted to without departing from the spirit of the invention or scopeof the subjoined claims.

What is claimed is:
 1. A grow line for supporting and moving plantsthrough a hydroponic garden environment in a controlled manner, whichgrow line comprises:a) a rotatable elongate cylindrical member providedwith a variable pitch helical groove along the length thereof; b) anelongate housing enclosing the cylindrical member and including alongitudinal slot in the wall of the housing, the slot extendingsubstantially for the length of the cylindrical member; c) at least oneplant holder for supporting a plant and engagement means carried by theholder for disposition within the longitudinal slot of the housing andengaging the helical groove of the cylindrical member for supporting theholder in a cantilever manner from the housing and moving the holderalong the grow line upon rotation of the cylindrical member; and d)conduit means carried by the housing and positioned substantiallythereabove, the conduit means including means for directing treatmentfluids from substantially above the housing outwardly and directly tothe undersides of the leaves of the plant supported by the holder. 2.The grow line of claim 1 further including means for supporting thehousing within the hydroponic garden environment and reinforcing meansdisposed between the housing and the support means for securing thehousing in position.